Limited preparation contextuality in quantum theory and its relation to the Cirel'son bound

TL;DR

This paper explores the limitations of preparation contextuality in quantum theory compared to more general theories and shows how this restriction underpins the Cirel'son bound on quantum nonlocality.

Contribution

It demonstrates that quantum theory's preparation contextuality is more limited than in general operational theories, linking this to the Cirel'son bound on nonlocality.

Findings

Quantum preparation contextuality is more restricted than in box world.

This restriction implies the Cirel'son bound on quantum nonlocality.

Quantum theory's limitations on contextuality underpin its nonlocality bounds.

Abstract

Kochen-Specker (KS) theorem lies at the heart of the foundations of quantum mechanics. It establishes impossibility of explaining predictions of quantum theory by any noncontextual ontological model. Spekkens generalized the notion of KS contextuality in [Phys. Rev. A 71, 052108 (2005)] for arbitrary experimental procedures (preparation, measurement, and transformation procedure). Interestingly, later on it was shown that preparation contextuality powers parity-oblivious multiplexing [Phys. Rev. Lett. 102, 010401 (2009)], a two party information theoretic game. Thus, using resources of a given operational theory, the maximum success probability achievable in such a game suffices as a \emph{bona-fide} measure of preparation contextuality for the underlying theory. In this work we show that preparation contextuality in quantum theory is more restricted compared to a general operational theory known as \emph{box world}. Moreover, we find that this limitation of quantum theory implies the quantitative bound on quantum nonlocality as depicted by the Cirel'son bound.